1. Field of the Invention
This invention relates generally to tools for installing helical coil inserts into tapped holes, and, more particularly, to tools having means for adjusting the depths to which such inserts are installed without requiring disassembling the front portion of the tool from the back end of the tool.
2. Description of the Prior Art
Helical coil inserts are commonly installed into tapped holes of a workpiece such that threaded fasteners, e.g., screws, thereafter can be held more securely. The inserts are frequently installed in relatively soft materials such as aluminum, to improve the gripping of threaded fasteners made of relatively hard materials such as various steel alloys.
Helical coil inserts of this kind are usually installed by compressing them into a smaller diameter and then rotatably threading them into the tapped holes. Once installed, the inserts expand from their compressed diameters and thereby press radially outwardly against the tapped holes and are held securely in place.
Tools for installing the helical coil inserts are typically driven by an air motor and include a tubular tool body having a threaded opening extending along its axis and having means at one end for carrying an insert. A mandrel is received within the threaded opening and is rotatably advanced by the air motor into engagement with the insert. Further advancement of the mandrel forces the insert through a prewinder, which reduces the insert's diameter, and from there into a tapped hole in an adjacent workpiece.
The insertion depth of the helical coil wire insert is controlled by limiting the distance to which the mandrel can be advanced. Typically, this has been accomplished using sleeve of a desired length which is positioned between the tubular tool body and a flange on the mandrel. In order to change the insert's installation depth, the mandrel had to be removed from the tool body and a different-length sleeve or spacer put in position around the mandrel. An exemplary tool of this kind is shown in U.S. Pat. No. 3,111,751 to Eddy.
The need to remove the mandrel from the tool body in order to adjust the insert's installation depth is unduly time consuming. This has been a particular problem when a large number of inserts have to be installed at a variety of depths.
Another approach has also been used previously, with equal difficulty. A stop collar has been used to limit the distance the mandrel could travel and thereby set the depth to which the helical coil insert could be installed. A set screw secured the collar in a selected position on the mandrel, but the collar would often slide up or down the mandrel after repeated use, because of vibrational forces and the force of the collar jamming against the tool body.
U.S. Pat. No. 4,768,270 to Czarnowski discloses an installation tool that quickly and conveniently allows the adjustment and setting of insertion depths without, inter alia, having to disengage the mandrel from the tool body. The tool includes a tubular tool body having a threaded opening extending along its axis and having means at its leading end for carrying a helical coil insert, in alignment with the threaded opening. A mandrel is located in the threaded opening for engagement with the insert, and driving means applies a torque to the mandrel sufficient to install the insert into a tapped hole. The tool further includes a sleeve threadedly received in the threaded opening of the tubular body, encircling the mandrel. The sleeve is engaged by an annular shoulder on the driving means, to prevent further advancement of the driving means and mandrel and thereby limit the depth to which the insert is installed in the tapped hole. The insertion depth can be adjusted by controllably threading the sleeve into or out of the tool body. The sleeve has two flats interrupting the threads, on opposite sides of the sleeve. A set screw threaded through the tubular body can be tightened against one of the flats to secure the sleeve's position within the tool body.
Although the tool disclosed in U.S. Pat. No. 4,768,270 provides significant advantages over prior installation tools, the fact that the front end assembly must be removed from the adapter to expose the slotted upper end of the sleeve to a spanner wrench which in turn grips and threadedly turns the sleeve into or out of the tool body increases the required set-up time during installation of the inserts into workpieces of various thicknesses.
There is thus a need for an installation tool for helical coil inserts that quickly and conveniently allows the adjustment and setting of insertion depths. In particular, there is a need for a tool that can be adjusted without having to disengage the mandrel driver from the rest of the tool body to reduce the setup times for insert installation.